Condition-responsive electric switch mechanism

ABSTRACT

A condition-responsive snap action electric switch mechanism, for use with a room air conditioner for instance, includes an operator which moves between extreme positions in response to a bellows. The bellows pressure increases and decreases in response to changes in temperature of the air passing over the evaporator. The switch also includes a first set of contacts to control energization of the compressor and a second set of contacts, including a snap-acting arm, to control energization of the evaporator and condenser fan motor. The operator includes an operating arm having a first portion which opens and closes the first set of contacts as the operator moves through a first, snap action, increment of travel between its extreme positions. The operating arm also includes a second portion which effects snap action of the snap-acting arm to open and close the second set of contacts as the operator moves through a second increment of travel separate from the first increment of movement.

Slonneger Mar. 7, 1972 CONDITION-RESPONSIVE ELECTRIC SWITCH MECHANISMJohn L. Slonneger, Morrison, 111.

General Electric Company Oct. 26, 1970 Appl. No.: 83,926

Related U.S. Application Data 1969, abandoned.

Continuation-in-part of Ser. No. 819,635, Apr. 28,

References Cited UNITED STATES PATENTS Atchison....

Canter Weber et a1.

Primary Examiner-Bemard A. Gilheany Assistant Examiner--Dewitt M. MorganAttorney-John M. Stoudt, Radford M. Reams and Ralph E. Krisher, Jr.

[57] ABSTRACT A condition-responsive snap action electric switchmechanism, for use with a room air conditioner for instance, includes anoperator which moves between extreme positions in response to a bellows.The bellows pressure increases and decreases in response to changes intemperature of the air passing over the evaporator. The switch alsoincludes a first set of contacts to control energization of thecompressor and a second set of contacts, including a snap-acting arm, tocontrol energization of the evaporator and condenser fan motor. Theoperator includes an operating arm having a first portion which opensand closes the first set of contacts as the operator moves through afirst, snap action, increment of travel between its extreme positions.The operating am also includes a second portion which effects snapaction of the snapacting arm to open and close the second set ofcontacts as the operator moves through a second increment of travelseparate from the first increment of movement.

9 Claims, 15 Drawing Figures PATENTED 7 2 SHEET 2 0F 3 INVENTOR. John L.S Ion/wager, BY {WM At tor/7:5

PATENTEDMAR 7 I972 SHEET 3 []F 3 FIG/5 MOVEMENT FIGJZ FIG. 15

F'IGJO INVENTOR. John L,. Slog/7 A t: Carney.

CONDITION-RESPONSIVE ELECTRIC swrrcn MECHANISM CROSS-REFERENCE TORELATED APPLICATION This is a continuation-impart of my copendingapplication Ser. No. 819,635 filedApr. 28, I969 and now abandoned.

BACKGROUND OF THE INVENTION This invention relates tocondition-responsive electric switch mechanisms and, more particularly,to such mechanisms for use with refrigeration systems.

Refrigeration systems such as, for instance, room air condi' tions arecustomarily controlled by a switch which cycles the compressor on andoff in response to the temperature of the air passing from heat exchangerelationship with the evaporator into the room. Thus the temperature ofthe enclosure or room is maintained at about a predetermined level.Often at night the outside temperature falls sufficiently that thecompressor may remain off for a long period. It still is desirable torun the evaporator and condenser fans to continue to bring in fresh airor circulate the air in the room. At times, such as the early morninghours, the ambient temperature falls sufficient that even circulation ofuncooled air is uncomfortable. Thus a temperature-responsive switch isused to control the evaporator fan. Often in the past entirely separateswitch mechanisms have been used for compressor and fan control. Thisrequires great care in calibration to assure that the fan always runswhen the compressor is energized. Prior art switch mechanisms using asingle temperature-responsive element to control both the compressor andthe evaporator fan have been so designed that sticking or erosion of thecontacts will cause undesirable changes in the sequencing of theswitching of the compressor and fan motors.

Also, in some cases it is desirable to have a multispeed fan which iscycled between various speeds of operation, with the compressor runningcontinuously, to provide maximum cooling. This further complicates thecontrol problem as it is desirable always to start the compressor inconjunction with a lowfan speed, and it is desirable that fanoperationwithout compressor operation be at low fan speed.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to provide a new and improved condition-responsive switchmechanism.

It is another object of this invention to provide such an improvedswitch mechanism, particularly for use with a room air conditionersystem, to control both the compressor and the motor for the evaporatorand condenser fans.

A further object of this invention is to provide an improvedtemperature-responsive switch mechanism, to control the operation of thecompressor and fan motor of an associated room air condition system,which is simple in design, rugged in construction and sure in operation.

A still further object of this invention is to provide an improvedcondition-responsive switch having at least two sets of contacts, inwhich operation of the various sets of contacts is always in the propersequence.

The invention, in one embodiment thereof, provides acondition-responsive switch comprising a first set of contacts includinga first stationary contact element and a first movable contact elementmounted on a movable arm for movement between contact open and closedpositions. The switch also has a second set of contacts including asecond stationary contact element and a second movable contact elementmounted on a snap-acting arm for snap action movement between contactopen and closed positions. A contact operator is mounted for pivotalmovement for selective engagement with the movable arm and thesnap-acting arm to effect opening and closing of the first and secondsets of contacts as the operator moves in opposite directions betweenfirst and second positions. The operator includes a toggle means forproducing a snap action increment of movement of the operatorintermediate its first and second positions. Condition-responsive meansis connected to the operator for effecting movement of the operatorbetween its first and second positions in response to predeterminedsensed temperatures. The operator effects opening and closing of thefirst set of contacts during its snap action increment of movement andeffects snap action movement of the snap-acting arm to open and closethe second set of contacts during an increment of movement of theoperator separate from its snap action increment of movement.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent, and theinvention itself will be better understood by reference to the followingdescription, taken in conjunction with the accompanying drawings,wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofan improved conditionresponsive switch mechanism embodying one form ofthe present invention;

FIG. 2 is an end view of the insulation base section of the switchmechanism, with some parts removed and some parts broken away forpurposes of illustration;

FIG. 3 is a side elevational view of the switch mechanism of FIG. 1,partially in section and partially broken away, illustrating certainoperational parts of the mechanism;

FIG. 4 is a somewhat schematic, partial side elevational view similar toFIG. 3, showing one position of certain operational parts of a switchmechanism incorporating another embodinient of the invention;

FIG. 5 is a view similar to FIG. 4, but showing the parts in anotherposition;

FIG. 6 is a diagrammatic view of a refrigeration system with which theswitch mechanism of the present invention is useful;

FIG. 7 is a schematic diagram of part of an electrical control systemfor the refrigeration system of FIG. 6, utilizing the switch mechanismof FIGS. 1-3;

FIG. 8 is a schematic diagram similar to FIG. 7 but utilizing the switchmechanism of FIGS. 4 and 5;

FIG. 9 is an end view, similar to FIG. 2, of the insulation base sectionof a switch mechanism incorporating yet another embodiment of theinvention;

FIG. 10 is a partial perspective view of the contact operator of theswitch mechanism shown in FIG. 9;

FIG. 11 is a somewhat enlarged schematic elevational view illustratingone position of certain operational parts of the switch mechanism ofFIG. 9;

FIG. '12 is a view similar to FIG. 11, but showing the parts in anotherposition;

FIG. 13 is a view similar to FIG. 11, but showing the parts in yetanother position;

FIG. 14' is a view similar to FIG. 11, but showing the parts in stillanother position; and

FIG. 15 illustrates force-movement operating characteristics of theswitch mechanism seen in FIG. 9 and is typical of such mechanisms whichincorporate that form of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, thereis shown a condition or temperature-responsive electric switch mechanism1 which embodies one form of the present invention, and often is alsoreferred to as a room air conditioner control. The exemplificationswitch 1 is an improvement in the general type of temperature-responsiveswitch disclosed in U.S. Pat. Nos. 3,065,323, issued to Charles Grimshawon Nov. 20, 1962; 3,065,320, issued to Richard W. Cobean on Nov. 20,1962; and 3,096,419,- issued to Louis .I. Howell on July 2, 1963; all ofwhich are assigned to General Electric Company, assignee of the presentinvention. Various aspects of such switch mechanism are shown in detailtherein.

The switch 1 includes an insulating base or housing 2 which, forexample, may be formed of molded phenolic thermosetting plastic, and aU-shaped frame 3, which is formed from a suitable material such asstainless steel and is securely mounted to the base 2 by some suitablemeans such as posts 4, which extend outwardly from each side of the baseand are securely received in mating openings 5 in the frame 3. The frame3 supports a bellows assembly 6 and a cover assembly 7, which includesmeans for mounting the switch upon a suitable supporting panel.

As best seen in FIGS. 2 and 3, the base 2 forms a housing for mountingthe various sets of contacts of the switch mechanism and theirassociated terminals. For instance, base 2 serves as a mounting forterminals 8a and 8b, the inner portions of which are contained in agenerally U-shaped internal cavity 9 of the base. The terminals 8a and8b are securely fastened to the base so as to provide stable externalconnections for associated wiring and a stable support for a first setof contacts generally indicated at 10. A set 10 of contacts includes astationary contact 11, having a contact element 12 electrically andmechanically connected to the terminal 8a by means of a stiff supportarm 13; and a movable contact 14, having a contact element 15electrically and mechanically connected to the terminal 8b by a movableor spring arm 16. The spring arm 16 biases the contact element 15 towardcontact element 12 so that the contacts 11 and 14 are biased to a closedposition.

The base or housing 2 also supports a second pair of terminals 17 and18. A second set of contacts generally indicated at 19 is mounted in thechamber 9 and includes a first or stationary contact 20 having a contactelement 21 electrically and mechanically connected to terminal 17 by arelatively stiff, return bent arm 22. The set 19 also includes a secondor movable contact 23 having a contact element 24 electrically andmechanically connected to the terminal 18 by snap-acting or spring arm25, including a toggle element 26. The spring arm 25 biases contactelement 24 toward contact element 21 so that the contacts 20 and 23 arebiased to a closed position.

As best seen in FIG. 3, a screw 27 is threadily received in the base 2and bears against the return bent arm 22 so as to assure properpositioning of the contact 20. As best seen in FIG. 2, a screw 18 isthreadily received in the base 2 to selectively and adjustably bearagainst the toggle element 26 and a screw 29 is threadily received inthe base 2 so as to selectively and adjustably bear against the movablecontact element 24 when the contact elements 21 and 24 are separated. Itwill be noted that the sets 10 and 19 of contacts are received in thecavity 9 in spaced-apart relationship and that the spring arms 16 and 25are substantially spaced apart and generally parallel.

The base 2, frame 3, bellows assembly 6 and cover 7 are securely joinedtogether to form the outer covering of the switch mechanism 1 formounting and protecting the various operative elements such as the setsof contacts 10 and 19. To this end the posts 4 are received in themating openings 5; the frame 3 is formed with tabs 30 which are bentover the cover 7, and springs clips 31 are positioned engaging the cover7 and bellows assembly 6. Other details of one manner of assemblingthese components may be had by reference to the aforementioned U.S. Pat.No. 3,065,323 Grimshaw and will not be described in further detail hereas those features of the exemplification switch mechanism form no partof the present invention.

Referring now particularly to FIG. 3, to actuate the sets of contactsthere is provided a contact operator 35 which includes a base portion 36with a contact operating arm 37 secured thereto by some suitable meanssuch as rivet 38 so as to extend into the cavity 9. The left end of baseportion 36 (as seen in FIG. 3) is supported by one end of a snap actiontoggle spring or toggle element 39. The other end of the toggle springis supported by a movable pivot member 40 which is supported by means ofa pair of channels 41. The channels 41 support the movable pivot member40 for longitudinal sliding movement within the base 2 and is moved by adifferential-adjusting screw 42. This provides a linearly movable,adjustable support for the left side of the toggle spring 39. The screw42 is threadily received in the base 2 and bears against the side of thepivot member 40 remote from the toggle spring 39 so that by adjustingthe position of the screw 42 the tension of the toggle spring 39 may beadjusted.

The operator 35 is also supported by means of a pair of shoulders 43which extend outwardly from each side of the base portion 36 and arereceived in cooperating slots 44 formed in the U-shaped frame 3. Thusthe operator 35 is mounted for pivotal movement about the engagement ofthe shoulders 43 with the slots 44, with the toggle spring 39continuously biasing the operator for movement in one direction, that isin a clockwise direction as seen in FIG. 3.

Spaced slightly forward from the shoulders 43, the base portion 36 isprovided with a pair of laterally disposed knife edges 45 which providearcuate pivots for supporting a bearing 46. The bearing 46 includesupper shoulders 47 which fit upon the knife edges 45 and depending,parallel pairs of struts 48. At their other ends, the struts 48 supporta cup-shape base 49. The knife edges 45, being positioned to the left ofthe pivot points of the shoulders 43, may be used for providing a forceon the operator 35 tending to rotate the operator in a counterclockwisedirection (as seen in FIG. 3). To this end a range spring 50 engages, atits lower end, a nut 51 in which is threaded an adjusting screw 52. Thelower portion of the screw 52 is provided with a shoulder portion 53which engages the base 49 of the bearing 46. Also the lower end 54 ofthe screw extends through the base 49 and is received in a cup 55 ofbellows 56. Thus the range spring 50, acting through the nut 51 andscrew 52, exerts a continuing force on the bearing 46 tending to rotatethe operator 35 in the counterclockwise direction. This force may beovercome by increasing the force which the bellows 56 exerts on thelower end 54 of the screw 52, which tends to lift the screw 52 andbearing 51 against the force of range spring 50.

The'increase and decrease of the force of the bellows 56 is utilized toprovide a response to a condition external to the switch mechanism suchas a sensed temperature. To this end the bellows is connected to a bulb57 by means of a capillary tube 58. The bellows, bulb and capillary tubecontain a charge of suitable vapor such as, for instance,dichlorodifluoromethane, butane or methyl chloride. Thus, as thetemperature of the bulb rises or falls, the pressure of the vapor chargeincreases or decreases. This causes a corresponding increase or decreasein the force exerted on screw end 54 by the bellows 56, all in thewell-known manner. Thus the pivotal movement of the operator 35 isresponsive to the condition external to the switch and, in the coldcontrol of the exemplification, it is responsive to a temperature sensedby the bulb 57.

By varying the compression of range spring 50 the sensed temperaturelevel at which the cold control operates may be adjusted. To this endthere is provided a manual adjustable cam 59 which is rotatablysupported on cover 7 by a shaft 60 with a spring washer 61 capturedbetween the cover 7 and a flange 62 formed on the shaft to retain theshaft and cam in a preset angular position. The cam 59 engages one end63 of a cam follower 64 which is pivotally mounted on the U-shaped frame3. The upper edge of the range spring 50 engages the underside of thecam follower 64 so that, as the cam follower responds to the rotarypositioning of the cam, the amount of the compression of the rangespring 50 between the cam follower and the nut 51 is changed. Also anopening 61a may be provided in cover 7 and a similar opening, not shown,in cam follower 64 for insertion of a screwdriver to calibrate themechanism by adjusting the screw 52.

As thus far described, the toggle spring 39 exerts a continuing force onthe operator 35 tending to cause it to rotate in a clockwise direction,and this force may be overcome by the range spring 50 to move theoperator 35 in a counterclockwise direction. The force of the rangespring'50 is opposed by the bellows 56 and is eflectively exerted on theoperator 35 only when the temperature sensed by the bulb 57 is below apredetermined level so that the force bellows S6 is reduced below apredetermined level.

Assuming, for purposes of explanation, that the mechanism is in theposition shown in FIGS. 2 and 3 and the bulb 57 senses an increasingtemperature, the pressure of the vapor charge will increase. This causesan increase in the force exerted on the lower screw end 54 by bellows56. This counters the force of range spring 50 and reduces the effectivecounterclockwise force exerted on operator 35. Eventually, at apredetermined sensed temperature, this counterclockwise force will bereduced sufficiently that toggle spring 39 will begin to pivot theoperator 35 in a clockwise direction. As is well-known, the more thetoggle spring moves the operator in this direction the stronger becomesthe effective force exerted by the toggle spring. Thus the operator issnapped in its clockwise direction. Similarly, as the bulb senses afalling temperature the vapor pressure. and thus the bellows force isreduced, and the effective counterclockwise force exerted on theoperator 35 by range spring 50 increases. Eventually, at a predeterminedsensed temperature, the range spring will begin to move the operator ina counterclockwise direction against the toggle spring 39. As is wellknown, the more the operator moves in this direction the weaker becomesthe effective force exerted by the toggle spring. Thus the operator issnapped back to the position shown in FIGS. 2 and 3.

The particular temperature at which the bellows will allow the rangespring 50 to overcome the toggle spring 39 is determined by the settingof the cam 59. The differential-adjusting screw 42 is used to set thedifferential of the mechanism; that is the difference between the sensedtemperature at which the operator will snap in one direction and thesensed temperature at which it will snap in the other direction.

The operating arm 37 is formed to cooperate with the contact sets and 19to effect opening and closing of the contacts in a predetermined manneras the operator pivots in its two directions. To this end the operatingarm 37 extends into the chamber 9 and includes a first portion or tang65 which overlies the free end of spring arm 16. The operating arm 37also includes a second portion or tang 66 which overlies the spring arm25. The portions 65 and 66 are spaced apart a distance which iscoordinated with the spacing of the spring arms 16 and 25 to provide aproper sequence of operation of the sets of contacts 10 and 19.

More specifically, when the sensed temperature is at or above apredetermined level, so that the operator 35 has been pivoted to itsextreme clockwise position, both the portions 65 and 66 are out ofengagement with the cooperating spring arms and both sets of contactsare closed. As the sensed temperature decreases, the force of bellows 57will decrease and the range spring 50, acting through the nut 51 andscrew 52 will exert an increasing counterclockwise force on the operator35. At a predetermined sensed temperature the effective counterclockwiseforce exerted on the operator 35 will be sufficient to overcome thetoggle spring 39, and the operator will snap in a counterclockwisedirection. This brings the tang 65 into engagement with spring arm 16and opens the contact elements 12 and 15. This counterclockwise snapaction is suft'rcient to bring tang 66 into engagement with spring arm25.

If the sensed temperature then begins to rise, the force exerted by therange spring 50 will be counteracted by an increasing force of thebellows 56 and at a second, slightly higher sensed temperature, theoperator 35 will snap in a clockwise direction releasing the spring arm16 so that the contact elements 12 and are again closed. Thus thecontact elements 12 and 15 are opened and closed as the operator 35moves through a first increment intermediate its extreme clockwise andcounterclockwise positions.

Assuming that after the contact elements 12 and 15 are opened the sensedtemperature continues to decrease, the vapor pressure decreases and theforce of bellows 56 decreases. This causes an increasing efiectivecounterclockwise force to be exerted upon the operator 35 and thus thespring arm 25. This force continues to increase until it is sufficientto overcome the toggle spring element 26, and the spring arm snapsdownward. This opens the contact elements 21 and 24, with the contactelement 24 coming to rest against the adjustable screw 29.

Thereafter, when the sensed temperature rises, the effectivecounterclockwise force exerted on the operator 35 decreases and, at afirst predetermined temperature, slightly above that at which thecontact elements 21 and 24 separated, the spring arm 25 will snapupwardly to close the contact elements 21 and 24. A furtherpredetermined increase in the sensed temperature will cause the contactelements 12 and 15 of contact set 10 to be snapped closed in the mannerdescribed above.

The adjustable screw 28, bearing against the toggle element 26 sets thesensed temperature at which the spring arm 25 will snap to its contactopen position while the adjustable screw 29 engaging the contact element24 in its contact open position determines the temperature differentialof the contact set 19; that is the differential in the temperature atwhich the contact elements 21 and 24 open and the temperature at whichthey close.

The spacing between the spring arms 16 and 25 and the spacing betweenthe operating arm portions or tangs 65 and 66 are coordinated so thatthe increment of travel during whichthe operating arm effects openingand closing of contact set 10 and the increment of'its travel duringwhich it effects opening and closing of the contact set 19 are separatedsufficiently that the contacts 11 and 14 may be cycled, that isrepeatedly opened and closed, without effecting thepositioning of thecontacts 20 and 23 and the contacts 20 and 23 cycled without effectingthe positioning of contacts 11 and 14. Also the contacts 20 and 23 willbe opened only when the contacts l1 and 14 are open and, in thoseinstances when both sets of contacts have been opened, the contacts 20and23 will always close before the contacts 11 and 14.

A switch mechanism embodying the present invention, such as thatdescribed above, is of substantial advantage as a cold control forcontrolling the operation of a refrigeration system such as, forinstance, an air conditioner. For purposes of illustrating its use insuch an environment there is shown in FIG. 6, in s'implified schematicform, an air conditioning system 70 for controlling the temperature in aroom or other enclosure 71. The system includes an evaporator or indoorcoil 72, a compressor 73, an outdoor coil or condenser 74 and arestricter 75, all connected together by suitable tubing to form acirculating system for a suitable refrigerant. The air conditioningsystem also includes an evaporator fan 76 driven by a suitable electricmotor 77 so that the fan 76 causes air to pass in heat exchangerelationship to the evaporator and then to be dischargedinto the room orenclosure 71. This air may be air which is recirculated within the roomor may be air drawn in from outside the enclosure. Normally the motor 77also will power a condenser fan for directing air across the condenser74.

FIG. 7 is an electrical schematic circuit diagram of a portion of acircuit for energizing the air conditioning system 70. The circuitincludes a pair of conductors 78 and 79 for connection to a suitablesource of electrical power, such as the normal household supply. Thecompressor 73 is connected between the conductors 78 and 79 in serieswith the contacts 11 and 14 of the'set of contacts 10. The evaporatorfan motor 77 is connected between the conductors 78 and 79 in serieswith the contacts 20 and 23 of the set of contacts 19. The bulb 57 willbe positioned to sense the temperature of the air being discharged fromthe evaporator 72 into the room or enclosure 71 so that, by suitablerotation of the shaft 60 the switch mechanism 1 may be set to maintain adesired temperature within the room.

As described above the operating arm 37 causes the contacts 11 and 14 tobe cycled between their opened and closed position as the operator 35moves through a first increment between its extreme positions under thecontrol of the condition-responsive mechanism. This cycling willenergize and deenergize the compressor 73 so that the air beingdischarged from the evaporator will have a temperature which oscillatesclosely about the temperature set by the shaft 60. It will be notedthat, during this operation, the fan motor 77 is continuously energized.In the event that the air discharged from the evaporator continues tofall, despite the fact that the compressor 73 is deenergized, thetemperature sensed by the bulb 57 will reach the point at which theoperating arm 37 causes the contacts 20 and 23 to be opened todeenergize the fan motor 77 and discontinue the flow of air. With airconditioning units this will tend to occur, for instance, in earlymorning hours when the outside temperature falls below the desiredoperating temperature of the air conditioning system. Continuedoperation of the fan 76 under such conditions, even without operation ofthe compressor 73, could cause an uncomfortable condition within theroom.

Thus the switch mechanism 1, under normal ambient conditions calling forrefrigeration, will cycle the compressor 73 so as to maintain the propertemperature within the enclosure, without cycling the fan and, when theambient conditions become such that refrigeration is no longer required,the entire system, including both the compressor and the fan, will bedeenergized to prevent unpleasant conditions within the enclosure.

It is often desired in refrigeration systems, particularly room airconditioners, to provide a multispeed evaporator fan which normallyoperates at a low speed but which is continuously energized at a highspeed or is cycled between a low and high speed to provide maximumcooling when necessary. FIGS. 4 and illustrate, in a somewhat schematicform, another embodiment of the present invention for providing suchmultispeed control. The embodiment of FIGS. 4 and 5 differs from that ofFIGS. 1 through 3 in the configuration of the operating arm and thenumber and positioning of the sets of contacts. Therefore, in describingFIGS. 4 and 5, the same reference numerals have been applied to thoseparts which remain basically the same. The mechanism is the same inFIGS. 4 and 5, differing only in that it shows the switch in two of itspositions.

Referring now to FIGS. 4 and 5, there is provided a first set ofcontacts 80 having a pair of stationary contacts 81 and 82 and a movablecontact 83. The contact 81 includes a contact element 84 which iselectrically and mechanically connected to a suitable terminal (notshown) SHOWN) by a stiff arm 85.

The contact 82 includes a contact element 86 mounted on a stiffconducting arm 87. The contact 83 includes a doublesided contact element88 which is connected to a suitable terminal (not shown) by a spring armor snap-acting arm 89, including a toggle element 90. A second set ofcontacts 91 is provided and includes a stationary contact 92, having acontact element 93 electrically and mechanically connected to a suitableterminal (not shown) by a stiff conducting arm 94; and a movable contact95 having a contact element 96, electrically and mechanically connectedto a suitable terminal (not shown) by a spring arm 97. There is a thirdset of contacts 98 which includes a stationary contact 99, having acontact element 100 mounted on and electrically connected to a stiff arm87, and a movable contact 101, having a contact element 102 which iselectrically and mechanically connected to a suitable terminal by aspring arm 103.

The operator 35a includes the base portion 36 and a somewhat modifiedcontact operating arm 37a. The operating arm 370 includes a firstportion or tang 104 which overlies the spring arm 97 and a secondportion in tang 105 which overlies both the spring arm 89 and the springarm 103.

Referring now to FIG. 8 there is illustrated an electrically schematicdiagram similar to FIG. 7 showing suitable connections for an airconditioning system utilizing the switch mechanism of FIGS. 4 and 5 inwhich the evaporator fan 76 is driven from a multispeed motor 77a. Onebranch circuit extends from conductor 78 to conductor 79 through thecontacts 92 and 95 of contact set 91 for energizing the compressor. Thecircuit for the evaporator fan motor 77a includes two branches. One ofthese extends through the contacts 81 and 83 of contact set 80 and thendirectly to the terminal of the motor 77a for providing high-speedoperation of the motor.

The other branch circuit extends through the contacts 82 and 83 of thecontact set and the contacts 99 and 101 of the contact set 98, and thento the terminal of motor 770 for providing low-speed operation. Thus thecontact set 91 controls energization of the compressor 23, the contactset 80 controls the speed of operation of the fan motor 77a and thecontact set 98 is effective selectively to energize the motor 77a, butonly when the contact set 80 is positioned for lowspeed operation.

The spacing of the tangs or operating arm portions 104 and 105 arecoordinated with the spacing of the spring arms 97, 89 and 103 toprovide the desired operation of the air conditioning system. Forpurposes of briefly describing this motor operation assume that thecompressor is energized and the fan is connected for energization forhigh-speed operation to provide maximum cooling. For this condition theoperator 35 is in its extreme clockwise position, not shown, so that thecontacts 92 and 95 are closed, the contacts 81 and 83 are closed and thecontacts 99 and 101 are closed. Asthe enclosure begins to cool and thetemperature sensed by the bulb 57 drops, the operator 35a will pivot ina counterclockwise direction. This causes the tang 105 to relax theforce exerted on spring arm 89, and the toggle element snaps the arm 89downwardly. This disconnects the contacts 81 and 83 ahd connects thecontacts 82 and 83, as shown in FIGS. 5 and 8. This shifts theconnection for the fan motor 77a to its low-speed terminal, as contactset 98 is closed, and the fan will begin operation at lower speed. If atthis time the temperature of the air discharged from the evaporator intothe enclosure rises, the operator 35a will be pivoted in its other orclockwise direction and move the contact 83 out of engagement with thecontact 82 and back into engagement with the contact 81, to againprovide high-speed operation of the fan. Thus, the fan will providemaximum cooling until a temperature within the enclosure is reached atwhich the desired temperature may be maintained by cycling of thecompressor, coupled to a lowspeed fan operation.

When this occurs the temperature of the air discharged from theevaporator will continue to drop after the fan has been shifted to alow-speed operation and an increasing counterclockwise force will beexhibited on the operator 35. This counterclockwise force will increaseuntil it overcomes the force of toggle spring 39 and snaps open the setof contacts 91, as shown in FIG. 4. This deenergizes the'compressor 23.Subsequently, normally the temperature of the air exhausted from theevaporator into the enclosure will tend to rise and the set of contacts91 will reclose, as shown in FIG. 5, to reenergize the compressor.Normally this mode of operation continues, with the cycling of thecompressor providing the necessary cooling to maintain the desiredtemperature as set by the shaft 60.

If, at some time as in early morning hours, the ambient temperaturefalls sufficiently, the temperature of the air exhausted from theevaporator will continue to fall, even though the compressor isdeenergized. The operator 35a will remain in the position shown in FIG.4 until the temperature drops a lower predetermined temperature. Acontinued decrease in the air temperature beyond this point will causethe contact set 98 to be opened to also deenergize the fan and preventunpleasant conditions within the enclosure.

A subsequent rise in the temperature of air in the enclosure will causethe bellows 56 to counteract the force of range spring 50 and rotate theoperator 35a in a clockwise direction so as to close the contact set 98and reenergize the fan for a low-speed operation. A continued rise inthe temperature in the enclosure will cause the operator 35 to snap fromthe position of FIG. 4 to that of FIG. 5 to reclose contacts 92 and 95to start the compressor. A continued rise in the temperature of the airexhausted from the evaporator into the enclosure will cause theclockwise force on operator 35a to continue to increase and eventuallymove contact 83 from contact 82 to contact 81 for shifting the fan fromlow-speed to high-speed operation.

The positioning of the spring arms 97, 89, and 103 is coordinated withthe shape of the operating arm 37a, particularly the spacing between thetangs 104 and 105, such that the increment of movement of the operator35a for cycling the fan motor 77a between .high and low speed, theincrement of movement of the operator 35a for cycling the compressor 23between its on and off conditions and the increment of movement of theoperator 35a for cycling the fan motor 770 between off condition and alow-speed operational condition are separated sufficiently thatthedesired sequence of operation is always provided. For instance thiscoordination is such that the speed of the fan motor is always shiftedtolow-speed operation prior to the compressor being deenergized, and thecompressor is always reenergized prior to the fan motor being shifted tohigh-speed operation. Also the fan motor is always shifted to low-speedoperation prior to being completely deenergized, and when energizedwithout energization of the compressor it is always energized for itslow speed of operation.

- If desired contact element 102 could be provided with a backside forcooperation with a stationary contact, not shown, to provide a stilllower speed of fan operation, rather an off.

Referring now to FIGS. 9-14, there is illustrated various features ofyet another embodiment of the present invention. With particularreference to FIG. 9 there is shown a base 110, which is very similar tobase 2, previously described, except that it is shaped to form a housingfor mounting three sets of contacts and their associated terminals. Forinstance, base 110 serves as a mounting for terminals 111 and 1 12, theinner portions of which are contained in a generally U-shaped internalcavity 113 of the base. The terminals 111 and 112 are securely fastenedto the base so as to provide stable external connections for associatedwiring and a stable support for a first set of contacts or switch meansgenerally indicated at 114. The set of contacts 114 includes astationary contact 115, having a contact element 116 electrically andmechanically connected to terminal 111 by means of a stiff support arm117; and movable contact 118, having a contact element 119 mechanicallyand electrically connected to terminal 112 by a spring arm 120. Thespring arm 120 biases the contact element 119 toward the contact element116 so that the contacts 115 and 118 are biased to the contact closedposition.

Base or housing 110 also supports additional terminals 121, 122, 123 and124. A stationary contact, in the form of a screw shaft 125 having acontact head or element 126 on one end is threadily received in terminal121 to electrically and mechanically connect the contact 125 to theterminal 121. An additional stationary contact 127 is threadily receivedin a stiff arm 128 which electrically and mechanically connects it toterminal 122. The contact 127 includes a pair of contact heads orelements 129 and 130 which are disposed on opposite sides of the arm128. A second movable contact 131 is provided and includes adouble-headed contact element 132 which is disposed between the contactelements 126 and 129. Contact element 132 is mounted on a snap-acting orspring arm 133 which electrically and mechanically connects the contactelement 132 to terminal 123. The snap-acting arm 133 includes a toggleelement 134 which causes the arm 133 to move with a snap action andbiases the arm 133 to a position in which contact element 132 engagescontact element 129. Thus, contact elements 126, 129 and 132 form a setof contacts with the movable contact being biased for engagement withone of the stationary contacts and movable to engagement with the otherstationary contact.

A third movable contact 135 is provided and includes a contact element136 electrically and mechanically connected to terminal 124 by asnap-acting or spring arm 137. The arm 137 includes a toggle element 138which causes the arm 137 to move with a snap action and biases arm 137to a position in which contact element 136 engages contact element 130.

A screw 139 is threadily received in the base 110 so as to selectivelyand adj ustably bear against movement contact element 136 when thecontact elements 130 and 136 are separated. A screw 140 is threadilyreceived in the base 110 to selectively and adjustably bear against thetoggle element 134. A third screw 141 is threadily received in the base110 and selectively and adjustably bears against the toggle element 138.In this regard it will be understood that the snap-acting or spring arms133 and 137, with their associated toggle elements 134 and 138, arereceived in the cavity 113 in spaced-apart relationship and that thearms 133 and 137 are generally parallel. As is known in the art, thesetting of screw 140 will determine the operating point or temperatureof snap-acting arm 133 while the spacing between contact elements 126and 129 will determine the temperature differential of snap-acting arm133. Similarly, the setting of screw 14] will determine the operatingtemperature of snap-acting arm 137 while the spacing between contactelement l30 and the end of screw 139 will determine the temperaturedifferential of snap-acting arm 137.

In order to actuate the sets of contacts there is provided a contactoperator 145 which may be essentially the same. as contact operator 35,previously described, except for a modified contact operating arm 146which extends generally at right angles to the base portion 36. Theoperating arm 146 includes a first portion or tab 147 and a secondportion or tab 148, which are spaced apart along the long axis of theoperating arm 146 and thus are spaced apart in the direction of movementof the operating arm. The portion 147 includes a lower edge 149 which isdisposed to engage spring arm while portion 148 includes an upper edge150, disposed to engage snap-acting arm 133, and a button or lower edge151, disposed to engage the snap-acting arm 137. In this regard thespringarms 120, 133 and 137 are spaced apart in the cavity 113 generallyin the direction of movement of the operating arm 146. It will beunderstood that the contact operator is designed to engage with and tobe operated by a bellows assembly, a range spring and a snap-actingspring means in the form of a toggle spring which may be identical withthe bellows 56, range spring 50 and toggle element or spring 39 shown inFIGS. 3-5, for instance. In fact such operating components and theirarrangement may be the same as previously described for otherembodiments of this invention and therefore will not be described orshown in detail with regard to this particular embodiment.

As discussed generally with regard to the other embodiments, such anarrangement of parts means that the operator 1.45, as it moves from oneof its extreme positions to the other, will have a first creep incrementof movement, then a snap action increment of movement and finally asecond creep increment of movement. The arms 120, 133 and 137 are soarranged with respect to each other and with respect to the contactoperating am 146 that the operating arm causes each of the snap-actingarms 133 and 137 to be actuated with a snap action during acorresponding one of the increments of creep movement of the contactactuator 145 while the spring arm 120 is engaged by the edge 149 toeffect opening and closing of the set of contacts 114 during the snapaction increment of movement of the operator 145.

, Assuming for purposes of illustration that the switch mechanism ofFIG. 9 is connected in an air conditioning control generally asindicated in FIG. 8 for the embodiment of FIGS. 4 and 5 and referringparticularly to FIGS. "-14, there now will be described a sequence ofoperation for the switch mechanism of FIG. 9. HO. 11 illustrates thecondition when the operator 145 is moved to its extreme positioncorresponding to the bellows 56 and bulb 57 sensing a predetermined lowtemperature, that is the compressor and the fan are both off. Assumingthe sensed temperature begins to rise, the pressure of the vapor chargein the bulb and bellows will increase. This increases the force exertedby the bellows in opposition to the range spring and reduces theeffective force of the range spring. As explained with regard to theembodiment of FIGS. 1-3, the toggle spring 39 beings to cause theoperator to move upwardly (as seen in FIG. 11) with a creeping motion.As the contact operator 145 creeps upwardly the button or edge 151,

which has been holding spring arm 137, gradually decreases the force itis exerting on arm 137 to a level where the arm 137 snaps upwardlybecause of the toggle element 138 so as to move contact element 136 intoengagement with contact element 130. When contact element 136 engagescontact element'130, the fan motor is energized on low speed.

Thereafter, if the bulb 57 continues to sense a rising temperature theoperator 145 will continue upwardly with a creep movement. If, however,for some reason such as drawing in cool outside air the bulb senses adecreasing temperature the operator will reverse itself and creepdownwardly. This will cause the button 151 to increase the force on thearm 137 until, at a calibrated force value corresponding to apredetermined sensed temperature it will effect a downward orcounterclockwise snap action of the spring arm 137 to disengage thecontact element 136 from contact element 131 and bring it intoengagement with screw 139.

Assuming the bulb senses a rising temperature the operator will continueto creep upwardly (as seen in FIGS. 11-14) until the forces acting onthe operator 145 pass through a balance condition and the toggle spring39 assumes control. The toggle spring then moves the operator 145upwardly through a second or snap action increment of movement. Thissnap action increment of movement carries the operator from the positionshown in FIG. 12, where button 151 is just engaging snap-acting arm 137,to the position shown in FIG. 13 where the edge 149 has released the arm120, so that it has closed contact elements 116 and 119 with a snapaction, and edge 150 has just come into engagement with snap-action arm133 but snap-acting arm 133 is still in its downwardly biased positionwith contact element 132 engaging contact element 129. Closing ofcontact elements 116 and 119 causes the compressor motor to be energizedto begin a refrigerating or air conditioning operation.

Thereafter, if the temperature falls the vapor pressure in the bellowsand bulb will fall and the forces acting on the contact operator 145will just over balance so that the contact operator 145 is snappedthrough its snap acting increment of movement in the other direction bythe toggle spring 39.

However, assuming the temperature sensed by the bulb 57 continues torise the vapor pressure will continue to increase and the contactoperator 145 will continue to move upwardly through its second creepincrement of movement so that the edge 150 exerts an increasing force onthe snap-acting arm 133 and, at an upper predetermined temperature thearm 133 will snap in a clockwise direction (as seen in FIGS. ll-14) sothat contact element 132 is moved from engagement with contact element129 to engagement with contact element 126. This shifts the fan motorfrom low speed to high speed. Thereafter the mechanism will shortlyreach mechanical stop and the compressor will run and the fan motor willrun at high speed so long as the temperatures above this higherpredetermined temperature are sensed.

As the temperature sensed by the bulb 57 falls the reverse occurs. Thatis, briefly stated, the contact operator 145 first moves through a creepincrement of movement from the position shown in FIG. 14 to the positionshown in FIG. 13, during which the force exerted by the edge 150 onsnap-acting arm 133 is reduced to a calibrated value at which arm 133snaps in a counterclockwise direction, moving contact element 132 fromcontact element 126 to contact element 129. This cuts the fan motor fromhigh to low speed. Thereafter the contact operator 145 is moved throughits snap action increment of movement from the position shown in FIG 13to the position shown in FIG. 12. During this increment of movement theedge 149 engages spring arm 120 and opens contact elements 116 and 119with a snap action. This deenergizes the compressor motor. Thereafter,the contact operator moves through a second increment of creep movementduring which the button or lower edge 151 of arm 146 increases the forceon snap acting arm 137 to effect a counterclockwise snap action of thatarm for moving contact element 136 out of engagement with contactelement 130. This completely deenergizes the evaporator and condenserfan motor so as to, in effect,

completely turn off the associated air conditioning unit.

Referring now particularly to FIG. 15 there is shown an illustration ofthe force-movement operating characteristics of I the mechanism of FIGS.9-14. This diagram is similar to-that shown and described in applicant'sprior US. Pat. No. 3,354,280 issued on Nov. 2l, 1967 and assigned toGeneral Electric Company, assignee of the present invention. Line 155illustrates the force-movement characteristic corresponding to the bulbsensing an increasing temperature. The mechanism starts at position A,which corresponds generally to the switch positions shown in FIG. 11.The operator moves through its first creep increment of movement whichcorresponds to curve A, B, C, B, D with the portionB, C indicating thesnap action movement of snap-acting arm 137. Point D illustrates thecondition at which the forces on the operator 145 become balanced andthe operator then snaps through its snap acting increment of movementindicated by curve D, E, F, G, G with portion E, F indicating theclosing of contact elements 116 and 119. Point G indicates the positionat which the forces acting on the contact operator l45 again becomebalanced and, assuming an increasing temperature, the operator thenmoves through its second increment of creep movement indicated by curveportion G, H, I, J with portion H, I indicating the snap action movementof snap-acting arm 133.

Now assuming a condition in which the switch is shown in theconfiguration generally indicated in FIG. 14 and assuming the bulb 57 tosense a falling temperature, curve J, L, M, N illustrates the firstcreep increment of movement of the contact operator 145 with L, Mshowing the snap-acting movement of snap action arm 133 from theposition in FIG. 14 to the position of FIG. 13. Position N indicatesanother balanced force condition on the operator 145 so that thereafterit snaps through its snap action increment of movement, illustrated bycurve N, O, P, R, R, with O, R indicating the opening of contactelements 116 and 119. At R the forces on the contact operator againbecome balanced, and assuming a continuing decreasing temperature theoperator will move through its second increment of creep movement, asillustrated by curve R, S, T, A with portion S, T illustrating the snapaction of snap-acting arm 137 from the position of FIG. 12 to theposition of FIG. 11.

While in accordance with the Patent Statutes, I have described what, atpresent, are considered to be preferred embodiments of my invention, itwill be obvious to those skilled in the art that numerous changes andmodifications may be made therein without departing from the invention,and it it therefore aimed in the appended claims to cover all equivalentvariations as fall within the true spirit and scope of the invention.

What I claim as new and desire to be secured by Letters Patent of theUnited States is:

1. A condition-responsive switch, comprising:

a. a first set of contacts including a first stationary contact elementand a first movable contact element mounted on a movable arm formovement between contact open and closed positions;

b. asecond set of contacts including a second stationary contact elementand a second movable contact element mounted on a snap-acting arm forsnap action movement between contact open and closed positions;

c. a contact operator mounted for pivotal movement for selectiveengagement with said movable arm and said snap-acting arm to effectopening and closing of said first and second sets of contacts as saidoperator moves in opposite directions between first and secondpositions;

d. said operator including snap-acting spring means for producing a snapaction increment of movement of said operator intermediate its first andsecond positions;

e. condition-responsive means connected to said operator for effectingmovement of said operator between its first and second positions inresponse to predetermined sensed temperatures;

f. said operator effecting opening and closing of said first set ofcontacts with snap action during the snap action increment of movementof said operator;

g. said operator effecting snap action movement of said snap-acting armto open and close said second set of contacts with snap action during anincrement of movement of said operator separate from the snap actionincrement of movement of said operator.

2. A switch as set forth in claim 1, wherein:

a. said movable arm is biased to one of its positions and is movable tothe other of its positions;

b. said snap-acting arm is biased to one of its positions and is movableto the other of its positions;

4 c. said operator includes a first portion overlying said movable armfor moving said movable arm to its one position and releasing saidmovable arm for return to its other position as said operator moves inopposite directions through its snap action increment of movement; and

d. said operator includes a second portion overlying said snap-actingarm for exerting a force on said snap-acting arm to effect snap actionmovement of said snap-acting arm to its one position and reducing theforce on said snap-acting arm to effect snap action movement of saidsnap-acting arm to its other position as said operator moves in oppositedirections through an increment of movement separate from its snapaction increment of movement.

3. A switch as set forth in claim 2, wherein: said snap-acting armincludes a toggle element biasing said snap-acting arm to one of itspositions and a first manually adjustable stop means engages said toggleelement for selectively adjusting the temperature sensed by saidcondition responsive means corresponding to the increment of movement ofsaid operator separate from its snap action increment of movement duringwhich said snap-acting arm moves between its switch open and closedpositions.

4. A switch as set forth in claim 3, wherein: said snap-acting arm,including said toggle element, provides a differential in temperaturesensed by saidcondition-responsive means at which said second set ofcontacts is opened and at which said second set of contacts is closed;said switch further including second manually adjustable stop means forengaging said snap-acting arm to limit opening movement of saidsnap-acting arm and thereby selectively adjust the temperaturedifferential.

5. A condition-responsive switch mechanism comprising:

a. first switch means having first and second switch positions;

b. second, snap-acting, switch means having first and second switchpositions;

c. third, snap-acting, switch means having first and second switchpositions;

d. contact operating means movable between first and second positions inactuating relation with said first, second and third switch means foreffecting operation of said first, second and third switch means;

e. condition-responsive means connected to said contact operating meansfor effecting movement of said contact operating means between its firstand second positions in response to predetermined temperatures;

f. said contact operating means including snap-acting spring means sothat movement of said contact operating means between its first andsecond positions includes a first creep increment, a snap actionincrement and a second creep increment;

g. said contact operating means being arranged with respect to saidfirst, second and third switch means so as to effect snap actionoperation of said first switch means during said snap action incrementof movement of said contact contact operating means. 6. A switchmechanism as set forth in claim 5 wherein at least one of said snapacting switch means includes a toggle element biasing it to one of itsswitch'positions and said mechanism further includes adjustable stopmeans engaging said toggle means for selectively adjusting thetemperature sensed by said condition-responsive means corresponding tothe operation of said at least one of said snap acting switch means.

7. A condition-responsive switch mechanism, comprising:

a. a first stationary contact, a first movable contact mounted on amovable arm, said movable arm being biased to a contact closed positionand movable to a contact open position; 1

b. second and third spaced-apart, stationary contacts, a second movablecontact mounted on a first snap-acting arm, said first snap-acting armbeing biased to a position with said second movable contact engagingsaid second stationary contact and movable to a position with saidsecond movable contact engaging said third stationary contact;

c. a fourth stationary contact, a third movable contact mounted on asecond snap acting arm, said second snapacting arm being biased acontact closed position and movable to a contact open position;

d. contact operating means movable between first and second positions;

e. condition-responsive means connected to said contact operating meansfor effecting movement of said contact operating means between its firstand second positions in response to predetermined temperatures;

f. said contact operating means including snap-acting spring means sothat movement of said contact operating means between its first andsecond positions includes a first creep increment, a snap actionincrement and a second creep increment;

g. said contact operating means including a contact operating armmounted in interfering relationship with said movable arm for effectingsnap action movement of said movable arm between its contact open andclosed positions during the snap action increment of movement of saidcontact operating means; i

h. said contact operating arm also being in interfering relationshipwith said first and second snap-acting arms for effecting snap actionmovement of said first snap-acting arm between positions with saidsecond movable contact in engagement with said second and thirdstationary contacts and for effecting snap action movement of said thirdsnap-acting arm between its open and closed positions as said contactoperating means moves through its first and second increments of creepmovement respectively.

8. A switch mechanism as set forth in claim 7, wherein said first andsecond snap-acting arms are spaced apart generally along the directionof movement of said operating arm and said operating arm includes aportion interposed therebetween for engaging said first snap-acting armduring said first creep increment of movement and for engaging saidsecond snap-acting arm during said second creep increment of movement.

9. A switch mechanism as set forth in claim 7, wherein at least one ofsaid snap-acting arms has a toggle element biasing it to one of itspositions and said mechanism further includes adjustable stop means forselectively adjusting the temperature sensed by saidcondition-responsive means corresponding to the operation of said atleast one of said snap-acting arms.

1. A condition-responsive switch, comprising: a. a first set of contactsincluding a first stationary contact element and a first movable contactelement mounted on a movable arm for movement between contact open andclosed positions; b. a second set of contacts including a secondstationary contact element and a second movable contact element mountedon a snap-acting arm for snap action movement between contact open andclosed positions; c. a contact operator mounted for pivotal movement forselective engagement with said movable arm and said snap-acting arm toeffect opening and closing of said first and second sets of contacts assaid operator moves in opposite directions between first and secondpositions; d. said operator including snap-acting spring means forproducinG a snap action increment of movement of said operatorintermediate its first and second positions; e. condition-responsivemeans connected to said operator for effecting movement of said operatorbetween its first and second positions in response to predeterminedsensed temperatures; f. said operator effecting opening and closing ofsaid first set of contacts with snap action during the snap actionincrement of movement of said operator; g. said operator effecting snapaction movement of said snapacting arm to open and close said second setof contacts with snap action during an increment of movement of saidoperator separate from the snap action increment of movement of saidoperator.
 2. A switch as set forth in claim 1, wherein: a. said movablearm is biased to one of its positions and is movable to the other of itspositions; b. said snap-acting arm is biased to one of its positions andis movable to the other of its positions; c. said operator includes afirst portion overlying said movable arm for moving said movable arm toits one position and releasing said movable arm for return to its otherposition as said operator moves in opposite directions through its snapaction increment of movement; and d. said operator includes a secondportion overlying said snap-acting arm for exerting a force on saidsnap-acting arm to effect snap action movement of said snap-acting armto its one position and reducing the force on said snap-acting arm toeffect snap action movement of said snap-acting arm to its otherposition as said operator moves in opposite directions through anincrement of movement separate from its snap action increment ofmovement.
 3. A switch as set forth in claim 2, wherein: said snap-actingarm includes a toggle element biasing said snap-acting arm to one of itspositions and a first manually adjustable stop means engages said toggleelement for selectively adjusting the temperature sensed by saidcondition responsive means corresponding to the increment of movement ofsaid operator separate from its snap action increment of movement duringwhich said snap-acting arm moves between its switch open and closedpositions.
 4. A switch as set forth in claim 3, wherein: saidsnap-acting arm, including said toggle element, provides a differentialin temperature sensed by said condition-responsive means at which saidsecond set of contacts is opened and at which said second set ofcontacts is closed; said switch further including second manuallyadjustable stop means for engaging said snap-acting arm to limit openingmovement of said snap-acting arm and thereby selectively adjust thetemperature differential.
 5. A condition-responsive switch mechanismcomprising: a. first switch means having first and second switchpositions; b. second, snap-acting, switch means having first and secondswitch positions; c. third, snap-acting, switch means having first andsecond switch positions; d. contact operating means movable betweenfirst and second positions in actuating relation with said first, secondand third switch means for effecting operation of said first, second andthird switch means; e. condition-responsive means connected to saidcontact operating means for effecting movement of said contact operatingmeans between its first and second positions in response topredetermined temperatures; f. said contact operating means includingsnap-acting spring means so that movement of said contact operatingmeans between its first and second positions includes a first creepincrement, a snap action increment and a second creep increment; g. saidcontact operating means being arranged with respect to said first,second and third switch means so as to effect snap action operation ofsaid first switch means during said snap action increment of movement ofsaid contact operating means and to effect snap action operation of saidsecond switch means and said third switch means during respective creepIncrements of movement of said contact operating means.
 6. A switchmechanism as set forth in claim 5 wherein at least one of said snapacting switch means includes a toggle element biasing it to one of itsswitch positions and said mechanism further includes adjustable stopmeans engaging said toggle means for selectively adjusting thetemperature sensed by said condition-responsive means corresponding tothe operation of said at least one of said snap acting switch means. 7.A condition-responsive switch mechanism, comprising: a. a firststationary contact, a first movable contact mounted on a movable arm,said movable arm being biased to a contact closed position and movableto a contact open position; b. second and third spaced-apart, stationarycontacts, a second movable contact mounted on a first snap-acting arm,said first snap-acting arm being biased to a position with said secondmovable contact engaging said second stationary contact and movable to aposition with said second movable contact engaging said third stationarycontact; c. a fourth stationary contact, a third movable contact mountedon a second snap acting arm, said second snap-acting arm being biased acontact closed position and movable to a contact open position; d.contact operating means movable between first and second positions; e.condition-responsive means connected to said contact operating means foreffecting movement of said contact operating means between its first andsecond positions in response to predetermined temperatures; f. saidcontact operating means including snap-acting spring means so thatmovement of said contact operating means between its first and secondpositions includes a first creep increment, a snap action increment anda second creep increment; g. said contact operating means including acontact operating arm mounted in interfering relationship with saidmovable arm for effecting snap action movement of said movable armbetween its contact open and closed positions during the snap actionincrement of movement of said contact operating means; h. said contactoperating arm also being in interfering relationship with said first andsecond snap-acting arms for effecting snap action movement of said firstsnap-acting arm between positions with said second movable contact inengagement with said second and third stationary contacts and foreffecting snap action movement of said third snap-acting arm between itsopen and closed positions as said contact operating means moves throughits first and second increments of creep movement respectively.
 8. Aswitch mechanism as set forth in claim 7, wherein said first and secondsnap-acting arms are spaced apart generally along the direction ofmovement of said operating arm and said operating arm includes a portioninterposed therebetween for engaging said first snap-acting arm duringsaid first creep increment of movement and for engaging said secondsnap-acting arm during said second creep increment of movement.
 9. Aswitch mechanism as set forth in claim 7, wherein at least one of saidsnap-acting arms has a toggle element biasing it to one of its positionsand said mechanism further includes adjustable stop means forselectively adjusting the temperature sensed by saidcondition-responsive means corresponding to the operation of said atleast one of said snap-acting arms.